Process for the manufacture of pentaenes



30-32 parts by Weight of vitamin A acetate crystals of melting point 57-5 8 C. are obtained.

EcrampleZ v 'l 50 parts by weight of 1-acetoxy3,7-dimethyl same manner as described in Example 1. About 8 parts by Weight of a yellow oil of nD221.600-t0.005 having a Vitamin A-acetate 'contentof- 80- 82 Volume of water are added to the mixture, whereupon the same is thoroughly stirred. The

aqueous layer is' separated, and the chloroform solution is again washed with 50 parts by volume per cent. (ultra-violet absorption measurement) j are obtained.

Example 3'l 50 parts by weight of L-diacetoxy-Sj-dlmethyl 9 (2*,6,6'-trimethyl-cyclohexene-(1")- yl) nonatriene-(2,4,7) are dissolved in 20 parts by volume of chloroform and` cooled to C. 300 partsby volume lof concentrated hydrochloric acid having a temperature of about -Sf C. are added while thoroughly stirring. After stirring fo114 minutes at about 0 C. the mixtureis briefly stirred with '400 parts by volume of ice water, the chloroform solution is quickly separated and vigorously stirred for 2li hours with 400 parts by volume of,w.ater `at.,20" C. At the beginning of this operation 0.5'opartr by Weight of d,lato copherol is added.v The aqueous layer isseparated off, thechloroform solutionl is .thoroughly washed with 20 parts by volume of a 5 per cent. sodium bicarbonate solution, 1 part by volume of pyridine and,v again 0.5 part byfweight of dba-,tocopherol is. added and the mixture is boiled down. under reduced pressure.V FinallyQthe mixture is heated in high vacuo at 40 C. until its weightremains constant.l About@ parts by weight of a yellow oilA of `11LD22 1.6000.005 having a vitamin A-acetate content of 'l0-'Hiper cent;A` (ultraviolet absorption measurement) are obtained.

,n i Example 4 5'0 .".parts by` weight of 1acetoxy-3,7vdimethyl 6 e hydroxy- 9- (2,6,6 -.`trimethylfcyclohexene-vv (1Q-yl)-nonatriene-(2,4,'7) are treated in lthe same manner 'as described inExample 3. About 47.8, parts by Weight of i a yellow oil of .111522 1 .'6`00i0-005ha'ving a vitaminA-'acetate content of '78-82 percent. v(ultraviolet absorption'ineasfurement) are obtained.

Example 5 parts weight of 1-acetoxye3fl-dimethyl'- l* -,hy'droxy 9 r(2,6,6 trimethyl'- cyclohexene- (l -yD- nonatrienef (2,4;7) are dissolved in.-100 parts by volume Vof chloroform, and the solution is cooled to 0 C.; 200 parts by Volume of concent1-ated lhydrochloric acid having a tempera'- ture ofr0 C. are added, andthe mixture is Vigorously` stirred during 3V minutes:- Then' Vthe chloroform layerjis separated. (After isolation;

thef'halogenocompound formed shows a. maxi# i' mumV at 283-28411@ in the ultra-violet absorption-spectrum, =20,000; the compound'V contains 1 'atom of; chlorine.)- 150 parts by volume of ofwater and subsequently with parts by volumeoof a5' per-cent. sodium bicarbonate solution.. All aqueous layers are successively extracted with 100 parts by volume of petroleum ether each." The united petroleum ether-chloroform solutionsare dried with sodium sulphate and boiled down at 60 C. under reduced pressure. 43-44 parts by Weight of a vitamin A- concentrateareobtained in the form of aviscous, yellow oilA of nD`22=1.603-1.606, and, -on` standing, said oil gradually crystallizes. The ultraviolet absorption measurement shows a vitamin A-acetate content of 88-90 per cent.

n Eample 7 o A solution of 1 part-by weight of l-acetoxy- 3,'7dimethyl`-6-hydroxy9 (2 ,6' ,6' '-trirnethyl-cyclohexene-(1')yl) -nonatriene-(ZA-fl) in 3 parts by weightof chloroform is vigorously .stirred for 3-7 minutes at. 0C. with 8.5 partsby'weight of concentrated hydrochloric acidl (fl-:1.6). A`The two 'layers 'areseparated the chloroform solution is quickly driedifover sodium sulphate, l' tered and therrstirred for-2 hours with 1 part by weightA of calcium oxide while cooling with water and then for 24 hours at'roornf'temperature undera nitrogen `atmosphere."-The calcium oxide is then ltered '01121015 per cent. dll (iL-tocopherol are added to the' filtrate, and the solution is Vthen extracted successively withV 2 parts by weight of 1.5,-n hydrochloric acid, saturated iksodium bicarbonate solution and water; After drying over sodium sulphate and further addition of 0.5 per cent. d,lx-tocopherol, the solution is boiled down under reduced pressure at V50-60"C.V Azconcentrate'contairng' ,'78 per cent.v vitami-nVYA-acetate isf obtained ina yield amounting'to" 95.5 per cent. By crystallizing from alcohol,` 60--7'70per cent. of the activity of crystals of `melting point 45-'50 C.

Athe'product-"may be obtained in the form of Example 8 A solution of 1 part by weight of 1palmitoxy 3,'l-dimethyl--hydroxy-Q- (2 ,6 ,6 -trimethyl-cyclohexene-(lj) -yl) -nonatriene-(ZAJ) in 5.2 parts byweight-of chloroform are vigorously stirred for 3-'7 minutes at 0C. with 7.2 parts by Weight of concentrated hydrochloric acid (d=1 .6). The two layers are separatedythe chloroform solution is quickly driedover sodium sulphate, ltered and then stirred fortwol hours with 1 part by weight of calcium oxide while cooling with water and then for 24 hours at room temperature under nitrogen atmosphere. Calcium oxide is then filteredoff, A0.5 `-per, cent. dba-tocopherol are added to the filtrate," Jwhereupon `the samef'fis successively: extracted with 2 parts by weight each of 1.5-n f'hydrochloricffacid, saturated sodium lbicarbonate solution and water.- After' drying .over sodium sulphate and further'additionfof; 0.5 per cent. yd,'1a.tocopherol, they solutionis boiled .down under-reduced pressure at 50'60."` C. A concentrate containing 68-'752per cent. of vitamin"A- palrtnita'te is thus obtained with a yield of 95 per Ceni".. L., V

We claim: l. Process of preparing pentaenes which comprises reacting in the cold a compound of the formula wherein R is selected from the group consisting of acyl and lower alkyl and R is selected from the group consisting of acyl and hydrogen, dissolved in a halogenated hydrocarbon having a large dipole moment in" the range of from about 1.18 18 e. s. u. cm. to about 1.7i 10"18 e. s. u. cm. and which is liquid under the operating conditions, with an aqueous hydrogen halide selected from the group consisting of hydrogen chloride and hydrogen bromide, and treating the resulting halogen compound, dissolved in va halogenated hydrocarbon having a large dipole moment in the range of from about l.18 1018 e. s. u. cm. to about 1.74 10"18 e. s. u. cm. and which is liquid under the operating conditions, with a dehydrohalogenating agent selected from the group consisting of water and basic substances.

2. A process according to claim 1, wherein the hydrogen halide is hydrobromic acid.

3. A process according to claim l, wherein the dehydrohalogenating step is performed in the wherein Hal is a halogen selected from the group consisting of chlorine and bromine and R is selected from the group consisting of acyl and lower alkyl, dissolved in a halogenated hydrocarbon having a large dipole moment in the range of from 'about 1.18 10-18 e. s. u. cm. to about 1.74X 10"-18 e. s. u. cm. and which is liquid under the operating conditions, by means of a reagent selected from the group consisting of water and basic substances.

8. A process which comprises Vdehydrobrominating a 1-acyloxy-3,7-dimethyl-8-bromo-9- (2,6',6' trimethyl cyclohexene (1') yl)- nonatriene(2,4,6) by treating the said compound, dissolved in a halogenated hydrocarbon having a large dipole moment in the range of from about 1.18 10*18 e. s. u. cm. to about 1.74 10-18 e. s. u Xcm. and which is liquid under the operating conditions, with water in the cold.

9. A process which comprises dehydrobrominating 1 acetoxy 3,7 dimethyl 8 bromo- 9 (2',6',6 trimethyl cyclohexene (1') yl) nonatriene(2,4,6) by treating the said compound, dissolved in a halogenated hydrocarbon 6 having a large dipole moment in the range of from about 1.18 1013 e. s. u. cm. to about 1.74 10-18 e. s. u. cm. and which is liquid under the operating conditions, with Water in the cold.

10. A process which comprises dehydrohalogenating a compound of the formula wherein Hal is a halogen selected from the group consisting of chlorine and bromine and R is selected from the group consisting of acyl and lower alkyl, dissolved in a halogenated hydrocarbon having a large dipole moment in the range of from about 1.18 1018 e. s. u. cm. to about `1.7l 1018 e. s. u. cm. and which is liquid under the operating conditions, by means of a basic substance.

11. Process of preparing pentaenes which comprises reacting in the cold a compound of the formula wherein R is selected from the group consisting of acyl and lower alkyl and R' is selected from the group consisting of acyl and hydrogen, dissolved in a halogenated hydrocarbon having a large dipole moment selected from the group consisting of chloroform, dichloromethane, dicli1oro ethylene, and chlorobenzene, with an aqueous hydrogen halide selected from the group con.- sisting of hydrogen chloride and hydrogen bromide, and treating the resulting halogen compound, dissolved in a halogenated hydrocarbon having a large dipole moment selected from the group consisting of chloroform, dichloromethane, dichloroethylene, and chlorobenzene, with a dehydrohalogenating agent selected from the group consisting of y water and basic substances.

12. A process which comprises dehydrohalogenating a compound of the formula wherein Hal is a halogen selected from the group consisting of chlorine and bromine and R is selected from the group consisting of acyl and lower alkyl, dissolved in a halogenated hydrocarbon having a large dipole moment selected from the group consisting of chloroform, dichloromethane, dichloroethylene, and chlorobenzene, by means of a reagent selected from the group consisting of water and basic substances.

HERBERT LINDLAR. RUDOLF REGG.

REFERENCES CITED The following references are of recordin the file of this patent:

UNITED STATES PATENTS Number Name Date 2,451,739 Isler Oct. 19, 1948 2,451,741 Huber Oct. 19, 1948 

1. PROCESS OF PREPARING PENTAENES WHICH COMPRISES REACTING IN THE COLD A COMPOUND OF THE FORMULA 